In recent year, a digital format in which a video data or an audio data is converted into digital signals for the transmission thereof has been attracted attention and has developed to practical use thereof. As compared to the analog format in the prior art, in the digital format, by such a data processing, the edition of programs or a post-production can easily be performed and data compression is allowed as desired, resulting in the production of various qualities of programs. For the recording medium, a personal computer internally arranged hard disk device or a digital versatile disk (DVD) is replaced with a video tape of analog format. Moreover, the transmission is of being through the Internet as a transmission medium and, as compared with the analog format, therefore, any desired information is easily available in all areas all over the country without “ghost image” that is undesirable double-image of a television picture, as well as, broadcast audience participation programs have been tried.
However, since, in the device for reproducing the television information stored in a recording medium, the digital video signals and the digital audio signals are separately processed, the difference between the reproduced video and the reproduced audio accompanied therewith will become a problem. While, since packet transmission in the Internet protocol is transferred through a large number of routers or network operating centers, there is an uncertainty to be added to the digital television information in the recording medium. Therefore, International Telecommunication Union (ITU) or International Electrotechnical Commission (IEC) recognizes the need for a method for more accurately measuring the time difference corresponding to the digital televisions. On the other hand, in the conventional signal processing for analog formats such as a high-definition, NTSC, and PAL formats, for example, the following methods have been proposed to detect and correct the difference between video and audio signals.
(1) Prior Art 1 (Patent Document 1: Japanese Patent Application Laid-Open Publication No. H07-38,771)
In order to adjust the difference between a dynamic image and the audio accompanied therewith, the technique in which a special signal format provided by inserting reference signals into respective dynamic image and the audio is objected has been disclosed.
(2) Prior Art 2 (Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2000-196,917)
In order to adjust the difference between a dynamic image and the audio accompanied therewith, the technique in which an analog format such as analog formats such as a high-definition, NTSC, and PAL formats is objected has been disclosed.
(3) Prior Art 3 (Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2002-165,153)
In order to adjust the difference between a dynamic image and the audio accompanied therewith, the technique to improve Prior Art 1, in which n analog format such as analog formats such as a high-definition, NTSC, and PAL formats is objected has been disclosed.
(4) Prior Art (Patent Document 4: Japanese Patent Application Laid-Open Publication No. 2003-158,643)
In order to adjust the difference between a dynamic image and the audio accompanied therewith, the technique which is different from either Prior Art 1 or Prior Art 2, in which n analog format such as analog formats such as a high-definition, NTSC, and PAL formats is objected has been disclosed.